SUBJECT: M.S. Thesis Presentation
BY: Carson Maki
TIME: Tuesday, May 2, 2017, 2:00 p.m.
PLACE: Van Leer Building, 218
TITLE: Quantification of Ultrasonic Shear Wave Scattering from an Element of a Compound Scatterer in a Bonded Plate via Wavefield Imaging
COMMITTEE: Dr. Laurence Jacobs, Co-Chair (ME)
Dr. Jennifer Michaels, Co-Chair (ECE)
Dr. Karim Sabra (ME)
Dr. Massimo Ruzzene (AE)


Ultrasonic nondestructive evaluation (NDE), which uses high-frequency acoustic waves to evaluate materials without compromising their integrity, refers to a family of techniques that are frequently implemented for detecting and characterizing defects in aerospace materials. Because of its potential for high-fidelity defect detection in a variety of applications, ultrasonic NDE research has largely focused on ultrasonic wave scattering from defects such as fatigue cracks and crack-like formations.

Angle-beam ultrasonic NDE uses an angled wedge to inject bulk waves into a material to interrogate the far surface and bulk of the material. Ultrasonic NDE techniques using angle-beam wedges coupled to piezoelectric transducers can be used to quantify a range of defects both in the bulk and on the surface of plate-like structures. However, little work beyond modeling has been done to quantify buried crack-like defects emanating from through-holes in layered plate-like structures, which are prevalent throughout several industries.

This work addresses ultrasonic shear wave scattering from buried defects emanating from through-holes in bonded metallic specimens. Methods are presented for segregating, analyzing, and quantifying scattering from a single element of a compound scatterer via ultrasonic wavefield imaging. A presented signal processing methodology is applied to wavefield data acquired via wavefield imaging, and various methods for quantifying ultrasonic shear wave scattering from crack-like defects are compared. Bonded plate specimen design and fabrication, wavefield measurement techniques, and analysis techniques such as frequency-wavenumber filtering, temporal and spatial windowing, and direct image analysis are also discussed.